The term 'Master' is hugely over-used in the UK. A guy can be a 'Master Painter', a 'Master Plasterer' or a 'Master Toilet Cleaner'. Just anything he dreams up, really. No qualifications. no exam, no certificate, no nothing. It mysteriously elevates him from being a bog-standard trader with 12 months on the job, into a mythical being who turns everything he touches into gold.
Fun fact = the term originated during the 15th and 16th centuries when cathedral-building was at its pinnnacle in Europe. The 'Master Stonemason' was the guy who oversaw the carving of critically-dimensioned stones for Gothic arches and similar, checking everything for dimensional accuracy - a kind of supervisor. Not an ordinarily-skilled guy with an exaggerated sense of his own importance and a desire to pull the wool over the eyes of gullible customers.